This invention relates to fabric washing machines of the type having a fabric receiving basket disposed within an outer tub, wherein fabrics are washed in the basket and washing liquid is continuously recirculated from the tub to the basket during wash and rinse operations. More particularly, the invention relates to an improvement in such machines in which the amount of water delivered into the machine during each fill operation is automatically determined by the size of the fabric load contained in the basket.
One type of fabric washing machine in which this invention is particularly advantageous is the domestic clothes washing machine. In such machines, the size of the load of clothes to be washed varies considerably; such machines may be used at full capacity, but may as well be used for substantially smaller loads. Clearly, using the amount of water necessary for a full load for only a small load results in water and energy being wasted in both wash and rinse cycles. On the other hand, using insufficient water for a relatively large load may result in poor wash results and possible damage to the clothes. Various common ways of solving this problem have required the user to estimate the approximate weight or volume of the clothes and select a water level accordingly. When the size of the load is correctly estimated, these approaches work satisfactorily. However, inaccurate load estimates may result in the aforementioned problems of excess water usage, inadequate washing action, and possible damage to the clothes.
It is desirable, therefore, to relieve the user of this burden by providing a washing machine in which the amount of water metered into the machine is automatically controlled to the proper amount to assure satisfactory washing and rinsing of the particular wash load without a need for user estimates. Commonly assigned U.S. Pat. No. 2,934,928, entitled "Clothes Washer with Means for Automatically Providing the Correct Water Level" issued to Winston L. Shelton, teaches one approach which employs a single ring of intermediate level apertures either in the outer basket wall or through the agitator center post to provide fluid communication between basket and tub. The packing density of the clothes load, is relied upon to impede the flow of liquid from the basket to the tub through the basket apertures during fill. When a sufficient head of liquid is accumulated in the basket, liquid flows from the basket to the tub at a rate which permits liquid to accumulate in the tub. Upon accumulation of a predetermined amount of liquid in the tub, the fill valve is closed, and agitation and recirculation begin. If, during the wash and rinse cycles, the liquid level in the tub drops below a second predetermined amount, agitation and recirculation stop and the fill valve again opens to provide additional liquid to the basket. This process is repeated through the wash and rinse cycles until sufficient liquid to wash the particular load as indicated by relieved packing is provided. Thus, the Shelton patent teaches use of the packing together of clothes, that is the packing density of the wash load, as the measure for controlling liquid level. In Shelton, either the inflow of fresh liquid or the recirculation of the liquid in the tub occurs continuously during wash and rinse operations, but not both simultaneously.
While the Shelton approach may work satisfactorily for loads comprised substantially of cotton fiber or other natural fiber fabrics, it has been empirically determined that loads comprised essentially of synthetic fibers due to their increased pliability, particularly in hot water, tend to pack together much more than natural fiber loads requiring more liquid in the basket to relieve the packing than is necessary for satisfactory wash results. Consequently, the Shelton approach would tend to over compensate for the size of such a load and use an excessive amount of washing or rinsing liquid in the basket.
Recognizing that a significant portion of modern wash loads generally include synthetic fabrics, it is desirable to provide a means for automatically controlling the liquid level in the basket which avoids the shortcomings of the prior art and which works satisfactorily for all types of fabric loads.
It is, therefore, a prime object of the present invention to provide a fabric washing appliance which automatically controls liquid level in the basket in accordance with the size of the fabric load to be washed independently of the packing density of the fabric for level control, and which works satisfactorily for both natural and synthetic fabrics.
It is a further object of the present invention to provide a fabric washing appliance which automatically controls the amount of liquid delivered into the appliance during each fill operation in accordance with the level of clothes or fabric received in the basket.
It is a further object of the present invention to provide a fabric washing appliance of the aforementioned type which permits agitation of the fabric in the basket only when a sufficient amount of liquid is present in the basket.